The present invention relates in general to container sealing equipment and, in particular, to an ultrasonic anvil cartridge for use in association with ultrasonic apparatuses for sealing containers having two or more layers of ultrasonic reactive material. While ultrasonic sealing can be utilized in connection with the sealing of many containers wherein at least two layers of ultrasonic reactive material are sealed together, one significant application is associated with the sealing of multi-wall valve bags.
Multi-wall valve bags have been used in the packaging industry for a number of years. These bags are generally filled with food products, agricultural products or chemical products for which delivery directly from the bag to another container, such as a mixing vat, is facilitated through the use of an extended sleeve attached to a valve located on the bottom of the bag. The addition of the sleeve also allows product manufacturers to fill the bags through the sleeve. Because the bag is filled through the sleeve, the remainder of the bag is pre-sealed by the packaging supplier, thus closure of the bag is simplified. The consumer uses the bag by positioning it with the sleeve disposed over a working container into which the user desires the bagged product flow. The user then opens the sleeve by removing its sealed portion, allowing the contained product to flow out in an orderly manner through the remaining portion of the sleeve and into the working container.
Multi-wall paper valve bags always had the potential to leak through the extended sleeve after filling. This leakage was attributed mainly to the sealing method employed. Originally, the sleeves were sealed by hand by flattening and folding the extended sleeve and then folding it back underneath the sleeve into the pocket, which results from the addition of the sleeve to the bag. Hand sealing is not considered dependable because it is wholly dependent on the skill and conscientiousness of the person performing the folding and sealing operations.
An attempted solution to this leakage problem was to coat the inner surface of the extended sleeve with thermoplastic materials. After filling the bag, a heater bar was pressed firmly against the sleeve to flatten it and then reactivate the thermoplastic coating on the sleeve interior. However, due to the coating of dust that often forms in the sleeve during the filling process this method was also considered unreliable. Dust (or even solid contaminant) reduces the effectiveness of any heat seal formed by the reactivated thermoplastic, unless the thermoplastic material is thick enough to enshroud the contaminate.
Another approach to the contaminant problem and sealing multi-wall valve bags has been to use ultrasonic energy to reactivate the thermoplastic. While the initial purpose of the ultrasonic vibrations was to increase the kinetic energy of the thermoplastic to heat it, the vibrations also move the contamination away from the area being sealed, thus allowing a more perfect seal and fewer bag failures.
Current ultrasonic sealing devices consist of an ultrasonic horn, which emits ultrasonic vibrations and an anvil which contacts the extended sleeve of a container such that the anvil supports the container, so that the horn can contact and pinch the bag shut.
While, this approach to sealing has greatly improved results, some aspects of the sealing device require excessive maintenance, particularly the anvil. These anvils currently utilize commercially available internal "C" type snap rings like those used in systems transmitting and/or dissipating various forms of energy. Because the anvil comes into close proximity to the ultrasonic horn, the C-rings experience substantial vibration. The resulting wear on these rings often necessitates their replacement approximately every two weeks in a normal commercial packaging operation. This involves the removal and replacement of approximately 200 C-rings. Such maintenance involves a significant amount of labor intensive time.
It is thus an object of the present invention to provide a unitary ultrasonic anvil cartridge which can be removed and installed in a fraction of the time required to replace the approximately 200 "C" type snap rings used in the prior art devices.
It is another object of the present invention to increase the useful life of the ultrasonic anvil, by encapsulating substantially C-shaped members in an elastomeric material, thus reducing internal friction, thereby extending their useful life. It is an associated object of the present invention to reduce the noise levels associated with the ultrasonic horn vibrating the anvil through dampening of the substantially C-shaped members through the use of an encapsulating material.
It is still a further object of the present invention to provide ultrasonic sealing of a multi-wall valve bag equal to or better than the sealing achieved with several hundred separate "C" type snap rings.
These and other objects of the present invention will become apparent in light of the present specification, claims and drawings.